Improvement in postage and revenue stamps



J. SANGSTBR. Postage and Revenue Stamp.

No. 220,092. Patented Sept. 30,1879.

witmzw, 5111mm UNITED STATES PATENT OFFICE.

JAMES SANGSTER, OF BUFFALO, NEW YORK, ASSIGNOR OF ONE-HALF OF HIS RIGHTTO ROBERT DUN BAR AND GEORGE H. DUNBAR, OF SAME PLACE.

I'MPEOVEMENT IN POSTAGE AND REVENUE STAMPS.

Specification forming part of Letters Patent N 0. 220,092, datedSeptember 30-, 1879 application filed July 9, 1877.

To all whom it may-concern:

Be it. known that 1, JAMES SANGSTER, of the city of Buffalo, in thecounty of Erie and State of New York, have invented certain new anduseful Improvements in Postage, Revenue, or other Stamps, whichimprovements are fully set forth in the following specification.

In the drawings, Figure 1 represents a finished stamp; and Fig. 2,apostage-stamp, showing the appearance of the same after an attempt hasbeen made to wash off the canceling-ink.

The object of. this invention is to produce upon portions ofthestamp-design a chemical change in the oily or other material which holdsthe particles of the coloring-matter of the ink together, so that whenan attempt is made to wash or otherwise erase the canceling-ink from thestamp for fraudulent reuse the parts so changed will wash out and exposethe attempt by destroy in g the appearance of the stamp; and it consistsof a postage or other stamp having lines, dots, or characters ruled orotherwise placed upon its surface, composed of a material thatuniteswith and changes the oily, fatty, or resinous matter in the ink,therebyforiiiingasoapy compound, or otherwise rendering it soluble inwater or other liquids in such lines or dots, withoutseriously injuringthe appearance of the coloring-matter therein. There are many of thealkalies that may be used for this purpose; but in practice-I find thatcaustic soda answersa good purpose. It ceases to be caustic in a shorttime after being put on, as it rapidly absorbs carbonic acid from theair and becomes carbonate ofsoda, after which it remains without change,and does not readily absorb water or become wet from the atmosphere,like caustic potash or its equivalent.

The caustic soda may be used in combination with many of the alkalies insuch proportions that the compound will be strong enough for thepurpose. I have used a solution of caustic soda and borax, which workedwell; aiso caustic potash, carbonate of ammonia, cyanide of potassium,and other alkaline solutions; but a solution of caustic soda and water,having a specific gravity of 1.356, or thereabout, answers a goodpurpose; but it may be further diluted with water and work well,according to the coarseness or fineness of the lines, very fine linesrequiring a stronger solution than coarser lines.

The depth at which the solution penetrates theiuk or paper may also beregulated by the width of the lines, as coarse lines hold agreaterquantity of the solution and will penetrate deeper into the ink andpaper than fine lines, which do not hold so much.

The stamp may be ruled or otherwise impressed with the solution oneither side; but such lines or dots should be coarse enough to holdsufiicient material to pass through the paper, so as to reach and actupon the material in the ink, as hereinbefore mentioned. When such linesare placed on the face of the stamp (which is better) it is notnecessary that the solution should pass through the paper, but only farenough to act on the ink. Consequently they may be made finer, orsufliciently narrow to produce the desired effect.

I claim as my invention A postage or other stamp having on its facelines, dots, or characters consisting of caustic soda, or other materialthat combines or unites with or changes the oily, fatty, or resinousmatter in the ink employed to form the design, as described, therebyproducing a soapy compound, or otherwise rendering the ink soluble inwater or other liquids, as specified.

JAMES. SANGSTER.

Witnesses HUGH SANGSTER,

O. L. Porn).

